Extraction recovery percentage

This is an important issue for the comparability of data, in particular for organic chemicals. Information about the percentage of extraction recovery, or at least, as a minimum requirement, information about whether or not correction for recovery has been applied to the results, should be provided to the customer. 

Selected plasma samples were analyzed by enzyme immunoassay and by a validated radioimmunoassay. An excellent correlation (r = 0.97 P < 0.01) was observed between the values obtained by both types of assays. The sensitivity of the assay as determined by the smallest amount of unlabeled hormone that was significantly different from zero was 10.0 pg per assay tube. In order to determine if nonspecific materials in the sample interfere with an accurate determination, 50, 100 and 200 pi of plasma samples from two males were assayed in triplicate. The parallelism exhibited by the groups had a correlation coefficient of 0.99 (P < 0.01). Mean concentrations of plasma testosterone were 4.4, 4.1 and 4.4 ng/mL for 50, 100, and 200 pi of plasma, respectively. Aliquots of a pool sample from a bull were assayed in the same assay (intraassay) and different assays (interassay). The intraassay and interassay coefficients of variation for 9 assays were 5.8% and 9.7%, respectively. The accuracy of the assay was tested by adding known amounts of testosterone to a constant volume (100 pi) of a low pool sample before extraction. The percentage recovery was 110%. Pool samples assayed both at the front and end of the assays averaged 3.3 and 3.5 ng/mL, respectively. 

The recoveiy percentage of CER using ASSWV was determined by employing healthy peanut leaf tissue spiked with standard CER. The application of standard addition method was used to determine the recovery percentage as well as the CER contamination level in infected extracts. 

The recovery percentage was 93.27 % with a relative standard deviation of 21.8 % at 1.04 x 10 mol dm level (n = 11). The LOD for a signal to noise ratio of 3 1 was about 6 ppb and the limit of quantification (LOQ) was about 50 ppb. The pondered relative standard deviation of 9.5 % was calculated for the ASSWV method. Results found for CER contamination level in extracts through the electroanalytical method were in reasonable agreement with those values determined by using HPLC measurements. 

The flavor compounds that are labeled with stable isotopes (isotopomers) differ only slightly from the analyte in terms of mass, and their physical and chemical properties—e.g., volatility, reactivity, distribution coefficient and chromatographic behavior—are the same as those of the unlabeled flavor compounds, with the exception of minor and negligible isotope effects. They are added to foods as internal standards as early as possible, namely before the first extraction, so that they undergo virtually the same losses as the flavor compounds to be studied during the isolation method and enrichment steps that are employed. For this reason, labeled compounds satisfy nearly all of the requirements for an ideal internal standard and can also tolerate workup methods with very low recovery percentages, provided that the detection sensitivity is not too low. 

A TLC method was developed for the estimation of nieotinie aeid and nicotinamide (Fignre 10.7) in phatmacentical preparations containing other vitamins, enzymes, herbs, and drugs, etc. [16]. The percentage recoveries for nicotinic acid and nicotinamide were 100.1 + 1.9 and 100.2 1.5, respectively, with this system. Each alcohol extract of samples or standard was pnt on sihca gel TLC plates, which were developed with distilled water. Each silica gel spot visualized under UV lamp was collected and extracted with 0.1 mol/1 HCl. The optical density of each clear extract was measured at 262 run. 

Accuracy (systematic error or bias) expresses the closeness of the measured value to the true or actual value. Accuracy is usually expressed as the percentage recovery of added analyte. Acceptable average analyte recovery for determinative procedures is 80-110% for a tolerance of > 100 p-g kg and 60-110% is acceptable for a tolerance of < 100 p-g kg Correction factors are not allowed. Methods utilizing internal standards may have lower analyte absolute recovery values. Internal standard suitability needs to be verified by showing that the extraction efficiencies and response factors of the internal standard are similar to those of the analyte over the entire concentration range. The analyst should be aware that in residue analysis the recovery of the fortified marker residue from the control matrix might not be similar to the recovery from an incurred marker residue. 

Solid-phase microextraction (SPME) consists of dipping a fiber into an aqueous sample to adsorb the analytes followed by thermal desorption into the carrier stream for GC, or, if the analytes are thermally labile, they can be desorbed into the mobile phase for LC. Examples of commercially available fibers include 100-qm PDMS, 65-qm Carbowax-divinylbenzene (CW-DVB), 75-qm Carboxen-polydimethylsiloxane (CX-PDMS), and 85-qm polyacrylate, the last being more suitable for the determination of triazines. The LCDs can be as low as 0.1 qgL Since the quantity of analyte adsorbed on the fiber is based on equilibrium rather than extraction, procedural recovery cannot be assessed on the basis of percentage extraction. The robustness and sensitivity of the technique were demonstrated in an inter-laboratory validation study for several parent triazines and DEA and DIA. A 65-qm CW-DVB fiber was employed for analyte adsorption followed by desorption into the injection port (split/splitless) of a gas chromatograph. The sample was adjusted to neutral pH, and sodium chloride was added to obtain a concentration of 0.3 g During continuous... 

A single SFE/ESE instrument may perform (i) pressurised C02 (SFE), (ii) pressurised C02/modifier and (iii) pressurised modifier (i.e. ASE /ESE , organic solvent) extractions. The division between SFE and ASE /ESE blurs when high percentages of modifier are used. Each method has its own unique advantages and applications. ESE is a viable method to conduct matrix/analyte extraction provided a solvent with good solvating power for the analyte is selected. Sample clean-up is necessary for certain matrix/analyte combinations. In some circumstances studied [498], SFE may offer a better choice since recoveries are comparable but the clean-up step is not necessary. 

C-labelled cholesterol was used to test the recovery of 5-100 pg of faecal sterols from seawater (labelled coprostanol not being available). The radioactivity of the samples and eluates was measured by a two-channel liquid scintillation counter. Percentage recovery was calculated on the basis of the amount of labeled material recovered in the acetone eluant. The results indicate that column extraction efficiency is not adversely affected by the salinity of the water samples, i.e., in the range 95-97%. 

Measurements are subject to systematic errors as well as the random errors covered in Section 4.3.2. Bias is the difference between the mean value of a large number of test results and an accepted reference value for the test material. The bias is a measure of trueness of the method. It can be expressed in a number of ways, i.e. simply as a difference or as a ratio of the observed value to the accepted value. This latter representation, when expressed as a percentage, is often termed recovery. This represents how much of the analyte of interest has been extracted from the matrix and measured. This is dealt with in Section 4.6.3. 

Recovery factor is defined as the percentage (i %), or fraction R, of the total quantity of a substance extracted under specified conditions. (In our text we also use percentage extraction, E%1)... 

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